diy solar

diy solar

Received new battery cells one is low

Bleedingblue

Solar Enthusiast
Joined
May 12, 2020
Messages
537
Out of 32 cells they all tested 3.28 but 1 cell that was 2.8. You think their is going to be any issues with the battery cell or just needs charging and then balancing?
 
I had one out of four similar to yours. Low cell had about 10% lower capacity. Not a huge deal on for but might be troubling on 32.
 
Do what you can to correct it but if it's truly bad, I would buy one cell from Amy Wan - if she still has any in her TX warehouse.
 
Out of 32 cells they all tested 3.28 but 1 cell that was 2.8. You think their is going to be any issues with the battery cell or just needs charging and then balancing?
I’m guessing this is for two 48 volt batteries. I could probably not skeep at night without testing the cell, and based off that would need to pass with flying colors, otherwise I would build the other batteries, and wait until the replacement cell came in.

I would top balance and test capacity test that cell, a test a couple of the other cells For a baseline. Let it rest overnight and check voltages in the morning. Probably won’t be 2.5 volts, but a little higher after the rest. Top balance the cells, let them rest 24 hours, and then check voltages and compare.

I don’t know the capacity of the cells, so this could take me a day and a half for 25 ah cells with a 10 amp charger, or several days with the same charger if the cells are 304 Amps.

Depending on the capacity test and resiting voltages, you can decide to use the cell and monitor. If you decide not to use them, could consider going after a refund on the one cell based off the data.

I have a couple of small batteries built now with 25 ah cells, and one has cells in where 5 tested at about 26 ah, and 3 tested at about 24.6 ah, with the greatest and least being 26% different in ah. I have no way to monitor these while on the battery, although they are hooked to a BMS that does not share any data, too cheap.

Honesty thought, would be tempting to see if the battery was available at that warehouse. The capacity testing is a lot of work.
 
I’m guessing this is for two 48 volt batteries. I could probably not skeep at night without testing the cell, and based off that would need to pass with flying colors, otherwise I would build the other batteries, and wait until the replacement cell came in.

I would top balance and test capacity test that cell, a test a couple of the other cells For a baseline. Let it rest overnight and check voltages in the morning. Probably won’t be 2.5 volts, but a little higher after the rest. Top balance the cells, let them rest 24 hours, and then check voltages and compare.

I don’t know the capacity of the cells, so this could take me a day and a half for 25 ah cells with a 10 amp charger, or several days with the same charger if the cells are 304 Amps.

Depending on the capacity test and resiting voltages, you can decide to use the cell and monitor. If you decide not to use them, could consider going after a refund on the one cell based off the data.

I have a couple of small batteries built now with 25 ah cells, and one has cells in where 5 tested at about 26 ah, and 3 tested at about 24.6 ah, with the greatest and least being 26% different in ah. I have no way to monitor these while on the battery, although they are hooked to a BMS that does not share any data, too cheap.

Honesty thought, would be tempting to see if the battery was available at that warehouse. The capacity testing is a lot of work.


Sounds like it. How do you capacity test? Got a 60 volt charger 5 amp charger and he said he was charging it up. I told him to charge it to 3.28v like the rest are.

Would the cell start bleeding power off sitting at an idle state by itself?
 
Would the cell start bleeding power off sitting at an idle state by itself?
Others smarter than me, but I would check that. I have two 25 ah batteries at 24 volts each. I’m working on two 24 volt 8S 280 ah battery packs with the first on the charger now. All my cells were delivered good, except one I physically damaged. That’s why I have the odd sized battery pack with the 24 ah to 26 ah capacity.

I’d top balance all the cells I capacity tested and check voltages 24 hours off the top balance.

Putting together these cells is not a quick process, so that’s why I’d want to let it rest before I add it.

This is how I did the capacity test, although I used the DL24P which is a slightly different than his.


I capacity tested all 16 of my 25 ah cells, whitch took about three to four days. I don’t plan on doing all my 280 ah cells. Those could take weeks. Right now for my 280 ah cells, I plan on doing 4. I did get these cells from a reputable vendor.

When I did the capacity test, the voltage auto shut off at 2.5 volts. After resting, overnight, the voltage climbed back up to 2.8. That lets me think this cell you have may be fully discharged. To me, the only way this could be fully discharged that ends in a good scenario, is if the vendor capacity tested this cell and forgot to charge it afterwards. Maybe it was a quality control measure that ends quality control checked. Other than that, I can’t think of a good reason for it to be completely discharge.

Even after all these tests are done, my eyes would be glued to the BMS to see how that cell is doing. With the charging process and at sunset, I’m looking at battery voltages of individual cells, so if those cells drift apart, that’s when it would DEFINITELY be time to swap the cell.

A03F37F2-AACF-4571-9FAB-B652195EA914.jpeg
All that work and waiting for the batteries, if I needed both batteries right away, I’d probably still do the tests I mentioned, ant if they did pass with flying colors, I‘d probably still order a replacement cell.
 
I told him to charge it to 3.28v like the rest are.
If charged to 3.28 like the others it will not be at the same charge level and will probably settle some. This would not really confirm anything.

Better to charge two in parallel to 3.5+ and see if the pair settles about the same. But then you have two out of balance from the set. Not sure this is best either.

Consider assembling the the whole battery with BMS and giving any low cells a boost at the end to the target voltage. Then need to run the battery down and see what holds up.
 
Back
Top